According to high integration and high densification of semiconductor devices, circuit wirings are microfabricated more and more, and the number of layers of multi-layered wirings is also increased. When it is intended to implement a multi-layered wiring while achieving microfabrication of a circuit, a step is increased following the surface unevenness of an underlayer. Thus, as the number of wiring layers is increased, a film coatability for a step shape (step coverage) is deteriorated in forming a thin film. Accordingly, a flattening of a semiconductor device surface becomes increasingly important in a semiconductor device manufacturing process.
Chemical mechanical polishing (CMP) is an important technique for flattening a semiconductor device surface. In CMP, the surface of a wafer is polished by bringing the surface of the wafer held by a substrate holding device called a top ring or a polishing head into a sliding contact with a polishing surface of a polishing pad and relatively moving the polishing table and the substrate holding device in relation to each other, while a polishing liquid containing abrasive grains of, for example, silica (SiO2) is supplied to the polishing surface of the polishing pad.
Here, when a relative pressing force between the wafer in the process of polishing and the polishing surface of the polishing pad is not uniform over the entire surface of the wafer, insufficient polishing or excessive polishing is caused depending on the pressing force imparted to the respective portions of the wafer. Thus, in order to uniformize the pressing force to the wafer, a pressure chamber formed by an elastic film is provided on the lower portion of the substrate holding device and a fluid such as, for example, air is supplied to the pressure chamber such that the wafer is pressed by the fluid pressure via the elastic film.
In manufacturing semiconductor devices, a polishing profile of a wafer edge has a significant influence on the yield of products. Thus, it is important to precisely adjust the polishing profile of the wafer edge. However, because the polishing pad is elastic, the pressing force applied to the edge (peripheral edge) of the wafer in the process of polishing becomes non-uniform, which may cause a so-called “edge drop” where an edge portion of the wafer is excessively polished.
Thus, for example, in a substrate holding device disclosed in Japanese Patent Laid-Open Publication No. 2013-111679, the elastic film is formed to have a flat region and a standing region positioned around the outer circumference of the flat region to be rising upwardly and vertically so that the pressing force to the substrate opposed to the standing region is locally reduced.